Tato diplomová práce je zaměřená na stabilizátory u podvozku aut. První část popisuje všeobecné znalosti vlivu naklonění karosérie na jizdní vlastnosti auta a možnosti konstrukčních řešení používaných v praxi. Dále jsou v této části uvedeny nevýhody použití stabilizátoru a jejich náhrady. Nasledující téma se zaměřuje na soutěž Formule Student a její všeobecná pravidla. Hlavní částí této práce je analýza stabilizátoru Formule Ford, na kterou v poslední části této práce navazuje analýza předního a zadního stabilizátoru Formule Student. Byly vytvořené kompletní MBS modely pro přední a zadní zavěšení včetně stabilizátoru. Díky těmto modelům bylo možné provést výpočty klopných tuhostí a pevnostní výpočty. Z těchto výpočtů bylo možné určit vhodné nastavení stabilizátoru. Všechny modely mohou být dále použitelné pro analýzu jízdních vlastností příslušného vozidla.

This thesis deals with the design of a dynamic model of a harmonic drive. It includes a theoretical study aimed at the analysis of the harmonic drive gearing principle and its nonlinear properties. The first part of the practical section deals with the analytical calculation of the nondeformed geometry of the Flexspline. Based on these results, several simulations in ANSYS are created to identify torsional characteristics of a harmonic drive. These simulation models are further enhanced by the analysis of clearance, backlash and inaccuracies and their impact on torsional properties. By using MATLAB /Simulink, several dynamic submodels are created representing the individual characteristics of nonlinearities in harmonic drives. Furthermore, a comprehensive dynamic model is created of the mechatronic system which is describing all nonlinearities and kinematic error of the transmission. The dynamic model is also experimentally verified based on its damping properties.

Driving with tyres not appropriate for the actual conditions can not only lead to accidents related to the tyres, but also cause detrimental effects on the environment via emission of rubber particles if the driving conditions are causing an unexpectedly high amount of tread wear. Estimating tyre performance in an online setting is therefore of interest, and the feasibility to estimate friction performance, velocity performance, and tread wear utilizing available information from the automotive grade sensors is investigated in this thesis. For the friction performance, a trend analysis is performed to investigate the correlation between tyre stiffness and friction potential. Given that there is a correlation, a model is derived based on the trend having a stiffness parameter as an input in order to predict the friction performance. Tendencies for a linear trend is shown, and a linear regression model is fitted to data and is evaluated by calculating a model fit and studying the residuals. Having a model fit of $80\%$, the precision of the expected values stemming from the proposed model is concluded to be fairly low, but still enough to roughly indicate the friction performance in winter conditions. A tread wear model that can estimate the amount of abrasive wear is also derived, and the proposed model only utilizes available information from the automotive grade sensors. Due to the model having a parameter that is assumed to be highly tyre specific, only a relative wear difference can be calculated. The model is evaluated in a simulation environment by its ability to indicate if a tyre is under the influence of a higher wear caused by a higher ambient temperature. The results indicates that the model is insufficient in an online setting and cannot accurately describe the phenomena of softer tyres having a larger amount of wear caused by a high ambient temperature compared to stiffer tyres. Lastly, a double lane change test (ISO 3888-2) is conducted to determine the critical velocity for cornering manoeuvres, which defines the velocity performance. The test was executed for six different sets of tyres, two of each type (winter, all-season, and summer). The approach to estimate the velocity performance in an online setting is analogue to that of the friction performance, and a trend analysis is performed to investigate the correlation between longitudinal tyre stiffness and the critical velocity. The results are rather unexpected and shows no substantial differences in velocity performance, even though the tyre-road grip felt distinctively worse for the softer tyres according to the driver. It is concluded that the bias stemming from the professional driver's skills might have distorted the results, and that another approach might need to be considered in order to estimate this performance.

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Machine tools accuracy has been a cornerstone in defining machining system capability and directly affecting dimensional and geometrical tolerance of machined parts. The effort for achieving higher precision and accuracy can be distinguished in two general ideas. One is to improve performance of machine tools by designing better, stiffer and more accurate machine tools. The other is to develop tools and methods for evaluating and measuring their behaviour and gain knowledge of their performance. In order to properly control the machine tool characteristics that can affect and improve their accuracy such as static stiffness and static accuracy.This thesis is aiming at establishing and further advancing the idea of loaded testing of machining systems and the concept of Elastically Linked Systems as a framework for measuring, identifying and characterising quasi-static stiffness of machine tools under loaded conditions. This will allow the creation of an improved capability profile of machining system accuracy. The focus is on the implementation of Elastically Linked Systems concept (ELS) through the Loaded Double Bar system, a measurement method that can partly simulate the process-machine interaction by reproducing forces exerted on the machine tool structure for the evaluation of system characteristics under loaded condition. This allows the qualitative and quantitative evaluation and comparison of machine tools for the purpose of accuracy enhancement, identification of weak directions with potential utilization in process planning, machine procurement and maintenance.Through two case studies, the capability to identify the effect of machine components and structure behaviour is shown. / <p>QC 20180514</p>

Introduction: The development of liver fibrosis is characterised by dramatic changes in the biomechanical composition and mechanical properties of the extracellular matrix (ECM). Increases in matrix stiffness associated with inflammation and fibrosis are implicated in promoting cancer development. Clinical studies have demonstrated a close association between increases in liver stiffness and the incidence of hepatocellular carcinoma (HCC). The effect of changes in matrix stiffness on tissue-resident hepatic progenitor cells (HPC) is unknown. Aberrant HPC proliferation has been implicated in the pathogenesis of HCC. It was hypothesised that changes in the stiffness of the cellular microenvironment are important in regulating the behaviour of liver-resident cell populations and may promote the development of HCC. Aims: i) to determine how changes in the stiffness of the cancer cell niche might regulate proliferation, differentiation and chemotherapeutic resistance in HCC; ii) to determine the relationship between changes in liver stiffness and hepatic progenitor cell (HPC) response in rodent models of chronic liver disease; and iii) to determine whether changes in the stiffness of the HPC niche regulate proliferation and differentiation in these cells. A secondary aim of the thesis was to characterise the pattern of histological changes observed in rodent models of chronic hepatic congestion and whether this might provide insight into the effect of oedema and congestion on the development of liver fibrosis. Methods: Cell culture experiments in HCC (Huh7/ HepG2) and HPC cell lines were performed using a system of ligand-coated polyacrylamide (PA) gel supports of variable stiffness. The stiffness of the PA supports (expressed as shear modulus) was altered across a physiological change (1-12kPa) corresponding to values encountered in normal and fibrotic livers. Thiacetamide and carbon tetrachloride (CCl4) models of liver fibrosis were used to investigate the relationship between increasing liver fibrosis, changes in matrix stiffness and HPC response. The pattern of histological changes in the liver in response to hepatic congestion was assessed in two unrelated murine models of dilated cardiomyopathy; the python and CREB S133A mice. Results: Increases in matrix stiffness, as would be encountered in liver fibrosis, promote HCC cell proliferation. Increasing matrix stiffness is associated with enhanced basal and hepatocyte growth factor-mediated signalling though ERK, PKB/ Akt and STAT3. Stiffness-dependent HCC cell proliferation is modulated by β1-integrin and focal adhesion kinase. Increasing matrix stiffness is associated with a reduction in chemotherapy-induced apoptosis in HCC cells. However, following chemotherapy there was an increase in the frequency of clone-initiating cells for cells maintained in a low stiffness environment. Flow cytometry in HepG2 cells demonstrated that culture in a low stiffness environment was associated with an increase in the frequency of the stem cell markers CD44, CD133 and CXCR-4. This effect was further enhanced in the presence of chemotherapy. There is a close association between HPC numbers and liver stiffness measurements in a rat CCl4 model of chronic liver fibrosis. The major expansion in HPC numbers in this model coincides with a similarly large increase in fibrous tissue deposition. In vitro experiments using PA supports demonstrate that increasing matrix stiffness promotes the proliferation of both primary murine HPCs and an immortalised HPC line (BMOL). Changes in matrix stiffness regulate the expression of hepatocyte and biliary markers in BMOL cells. Histological studies in both the Python and CREB S133A models reveal findings consistent with acute on chronic cardiac hepatopathy (ischaemic hepatitis). Features of chronic passive congestion and centrilobular necrosis are present concurrently and develop rapidly. Bridging fibrosis and cirrhosis are not present. Conclusions: Physiologically-relevant changes in matrix stiffness regulate proliferation, differentiation, chemotherapeutic-resistance and stem cell marker expression in HCC cells. Similarly, increases in matrix stiffness are closely correlated to HPC response in vivo and regulate HPC proliferation and differentiation in vitro.

Cardiovascular disease is common in Chronic Obstructive Pulmonary Disease (COPD), and forced expiratory volume in one second (FEV1) independently predicts cardiovascular morbidity and mortality. Pathological changes in the systemic vasculature have been proposed as potential mechanisms linking COPD to cardiovascular disease, and patients with COPD may be at increased risk of acute myocardial infarction during acute exacerbations. Notwithstanding causation, FEV1 may be a useful prognostic marker in patients undergoing cardiac surgery. This thesis examined these three aspects of cardiovascular co-morbidity in relation to COPD and FEV1. In 2,241 consecutive cardiac surgery patients, FEV1 was associated with length of hospital stay (p<0.001) and mortality (p<0.001) adjusting for age, sex, height, body mass index, socioeconomic status, smoking, cardiovascular risk factors, chronic pulmonary disease, and type/urgency of surgery. In a survey of Scottish Respiratory Consultants there was no consensus regarding the investigation and management of acute coronary syndrome in exacerbation of COPD. In a case-series of 242 patients with exacerbations 2.5% (95% CI 1.0 to 5.6%) had chest pain, raised serum troponin and serial electrocardiogram changes suggestive of acute coronary syndrome. However, over half reported chest pain, while raised troponin was not associated with chest pain or serial ECG changes. Carotid-radial pulse wave velocity (PWV), aortic distensibility, and aortic calcification were measured to assess the relationship of the systemic vasculature to FEV1 and emphysema severity on CT. In adjusted analyses, emphysema was associated with PWV in patients with COPD (p = 0.006) and, in population based samples, with extent of distal aortic calcification (p=0.02) but not with aortic distensibility (p=0.60). This thesis found that FEV1 was associated with mortality and length of hospital stay in patients undergoing cardiac surgery, and that chest pain and raised troponin were common but unrelated in exacerbation of COPD. In the vascular studies distal but not proximal vascular pathology was associated with FEV1, and if COPD is truly related to systemic arterial disease, the distal arterial tree is implicated.

Composite materials are being widely used in light weight structural applications due to their high specific stiffness and strength properties. However, predicting their mechanical behaviour accurately is a difficult task because of the complicated nature of these heterogeneous materials. This behaviour is not easily modeled with most of existing macro mechanics based models. Designers compensate for the model unknowns in failure predictions by generating overly conservative designs with relatively simple ply stacking sequences, thereby mitigating many of the benefits promised by composites. The research presented in this dissertation was undertaken with the primary goal of providing efficient methodologies for use in the design of composite structures considering inherent material variability and model shortcomings. A micromechanics based methodology is proposed to simulate stiffness, strength, and fatigue behaviour of composites. The computational micromechanics framework is based on the properties of the constituents of composite materials: the fiber, matrix and fiber/matrix interface. This model helps the designer to understand in-depth the failure modes in these materials and design efficient structures utilizing arbitrary layups with a reduced requirement for supporting experimental testing. The only limiting factor in using a micromechanics model is the challenge in obtaining the constituent properties. The overall novelty of this dissertation is to calibrate these constituent properties by integrating the micromechanics approach with a Bayesian statistical model. The early research explored the probabilistic aspects of the constituent properties to calculate the stiffness characteristics of a unidirectional lamina. Then these stochastic stiffness properties were considered as an input to analyze the wing box of a wind turbine blade. Results of this study gave a gateway to map constituent uncertainties to the top-level structure. Next, a stochastic first ply failure load method was developed based on micromechanics and Bayesian inference. Finally, probabilistic SN curves of composite materials were calculated after fatigue model parameter calibration using Bayesian inference. Throughout this research, extensive experimental data sets from literature have been used to calibrate and evaluate the proposed models. The micromechanics based probabilistic framework formulated here is quite general, and applied on the specific application of a wind turbine blade. The procedure may be easily generalized to deal with other structural applications such as storage tanks, pressure vessels, civil structural cladding, unmanned air vehicles, automotive bodies, etc. which can be explored in future work. / Graduate / 0548 / enginer315@gmail.com